Abstract
The thermal diffusivities of POCO graphite AXM-5Q1 and isotrophic graphite IG-110, the candidate graphite material for a High-Temperature Engineering Test Reactor (HTTR), were measured from room temperature to around 2000°C by laser flash method. The thermal conductivities of these materials were also calculated using the literature values of heat capacities. AXM-5Q1 showed a little different behavior at around room temperature to 100°C comparing with the results previously reported in the literatures, whereas at high temperatures it showed almost the same values. Measurements on IG-110 graphite were made on the specimens cut from two graphite blocks, and the mean value and its standard deviation were determined. Measurements were also made on neutron-irradiated IG-110 as well. The conductivities were found to decrease after irradiation and a different temperature dependence was observed. They showed a peak at around 200°C, the degree of the decrease depending on irradiation condition. It was considered that the shift of the peak was caused owing to the degradation of crystallites by neutron irradiation.
